Si2401
24
Preliminary Rev. 0.9
The hardware reset pin, RESET (Si2401, pin 8), is used
to reset the Si2401 to factory default settings.
z
Wakeup on Ring (lower-case z)
The Si2401 enters a low-power mode in which the DSP
and microcontroller are powered down. In this mode,
only the line-side device (Si3010) and the isolation
capacitor communication link are functional. An
incoming ring signal or line transient causes the Si2401
to power up and echo an “R”. Any character received on
the RXD pin also causes the Si2401 to exit the wakeup-
on-ring state. Return from wake-on-ring can also be set
to trigger the INT pin by setting S08[6] (WORM) = 1.
Alarm Industry AT Commands
The Si2401 supports a complete set of commands
necessary for making connections in security industry
systems. The Si2401 is configurable in two modes for
these applications. The first mode uses DTMF
messaging and is selected with the “!1” command. The
second mode uses FSK transmit with a tone
acknowledgement and is selected with “!2”.
The following are a few general comments about the
use of “!” commands. Specific details for each command
are given below. The first instance of the “!” must be on
the same line as the ATDT or ATDP command. DRT
must be set to data mode (SE4[5:4] (DRT) = 0
b
) before
attempting to send tones after a “!” command. The three
data-mode escape sequences (“+++”, “escape” pin and
“ninth-bit”) only function in “!2” mode. However, using
the “+++” or “ninth-bit” is not recommended because
characters could be sent to and misinterpreted by the
remote modem. Only the “escape pin” (Si2401, pin 14)
is recommended for use in the “!2” mode. The “!1” mode
has a special escape provision described below. The AT
commands for Alarm Industry applications are
described in Table 13.
!1
Dial number and follow the DTMF security protocol.
The format for this command is as follows:
ATDT<phone number>!1<message 1><CR>
K
!<message 2><CR>
K
!<message 3><CR>
K
K
!<message n><CR>
The modem dials the phone number and echoes “r”
(ring), “b” (busy), and “c” (connect) as appropriate. “c”
echoes only after the Si2401 detects the Handshake
Tone. After a 250 ms delay, the modem sends the
DTMF tones containing the first message data and
listens for a Kissoff Tone. If a Kissoff Tone shorter than
or equal to the value stored in S36(KTL) (default = 1
second) is detected, the Si2401 echoes a “K”. A “k” is
echoed if the length of the Kissoff Tone is longer than
the S36(KTL) value. The controller can then send the
next message. All messages must be preceded by a “!”
and followed by a <CR> and received by the Si2401
within 250 ms after the “K” is echoed. Setting
S0C[0] (MCH) = 1 causes a “.” to be echoed when the
DTMF tone is turned on and a “/” character to be
echoed when the DTMF tone is turned off. This helps
the host monitor the status of the message being sent.
The previous message can be resent if the host
responds with a “~” after the Si2401 echoes a “K”. Any
character other than a “!” or a “~” sent to the modem
immediately after the “K” causes the modem to escape
to the command mode and remain off-hook. Any
character except “!” and “~” sent during the transmission
of a message causes the message to be aborted and
the modem to return to the command mode.
If the Kissoff Tone is not received within 1.25 seconds,
the modem echoes a “^”. A “~” from the host causes the
last message to be resent. Any character other than a
“!” or a “~” sent to the modem immediately after the “^”
causes the modem to escape to the command mode
and remain off-hook.
!2
Dial the number and follow the “SIA Format” protocol for
Alarm System Communications.
The modem dials the phone number and echoes “r”
(ring), “b” (busy), and “c” (connect) as appropriate. “c”
echoes only after the Si2401 detects the Handshake
Tone and the speed synchronization signal is sent. The
signaling is at 300 bps, half-duplex FSK. The host can
Table 13. AT Command Set Extensions
for the Alarm Industry
Command
Function
!1
Dial and switch to DTMF security
mode
!2
Dial and switch to “SIA Format”
X1
SIA half-duplex mode search
X2
SIA half-duplex return online as
transmitter
X3
SIA half-duplex return online as
receiver
